The Research On Submergence Tolerance Comparison Of Rice At Tillering Stage And Alleviate Effects Of Exogenous Spermidne On Submergence Damage

Rice is an important food crop in our country.Flood disaster occurred frequently in rice growing season according to the exceed rainfall,which would bring a serious threat to rice production in the midstream and downstream of Yangtze River.Therefore,it has an important meaning to research the influence of submergence stress on rice growth and the damage mechanism,and put forward the corresponding mitigation technology to reduce flooding loss.Spermine(Spd)is a new type of growth regulating substances,plays an important role to enhance plant resistance and relieve stress injury.In this research,we used 36 rice cultivars popularized in downstream of Yangtze River as experiment materials,establishing an method to evaluate flood resistance ability of different varieties.On this basis,the rice(ningjing3 and zhendao 11)was used to study the effect of submergence stress of different time on growth and physiological characteristics.In order to provide a theoretical basis and technical support for flooding resistance cultivation,the rice was also used to study the alleviate effect of Spd on growth,physiological charactaistics and yield after submerged for 1,3,5,7 days at tillering stage.The results were shown:1.According to the indicators like green leaves loss rate,tillers loss rate,aboveground dry mass loss rate,yield loss rate and death rate,36 varieties were divided into sensitive type,intermediate type and resistant type to submergence through cluster analysis.The results showed that the stem and the upper three leaves under submergence stress were elongated comparing with CK.And the elongation of different types was shown as,resistant type rice>intermediate type rice>sensitive type rice.As to the number of tillers,green leaves and the aboveground dry mass,the reduction of resistant type rice was the lightest,while the loss rate of intermediate type was all between resistant type rice and sensitive type rice.The loss rate of yield and effective panicles in resistant type rice was significantly lower than the other type rice.For intermediate type rice,the loss rate of effective panicles,seed setting rates and 1000-grain weights were all significantly lower than sensitive type rice.2.The green leaves,tillers and aboveground dry mass of rice were significantly inhibited by submergence stress.The effective panicles and spikelets per panicle decreased significantly,which finally resulted in a significant falling in yield.A large number of ROS accumulated under submergence,the O2-· generation and H2O2 content increased significantly with prolonged submergence time.With the damage of ROS,the chlorophyll content of rice decreased,while the MDA content increased.In order to adapt to the submergence environment,the antioxidant enzyme SOD,POD and GR activities increased at first,but decreased as the submergence time prolonged.In conclusion,rice was less affected when suffering submergence under 3days,but damaged irreversible while submerged for more than 5 days.3.Spraying Spd on leaves at a concentration of 0.5 mM alleviated submergence-mediated growth reduction.It also significantly restored chlorophylls damaged in submergence,decreased the rate of O2-· generation and H2O2 content,and inhibited submergence-induced lipid peroxidation.Spd helped to maintain antioxidant enzyme activities after drainage,such as SOD,POD and GR,which ultimately improved the recovery ability of submerged rice.With the effect of Spd,the yields of submerged rice increased by 12.1%,17.9%,13.5%and 18.0%,respectively.It is supposed that exogenous Spd effectively alleviated oxidative damage caused by submergence stress,and significantly increased the submerged rice yield.